OREGON STUDY: Ritalin May Improve Parkinson's Symptoms, OHSU Study Says

[Murray Charters <mcharters@xxxxxxxxxxxxxx>]

Ritalin May Improve Parkinson's Symptoms, OHSU Study Says
Public release date: 6-May-2004
Contact: Jonathan Modie
modiej@xxxxxxxx
503-494-8231
Oregon Health & Science University

Ritalin may improve Parkinson's symptoms, OHSU study says
But active ingredient in antidepressant Paxil has no effect on physical symptoms
PORTLAND, Ore. ? A well-known drug used to treat hyperactive children boosts 
the potency of another drug that reduces
Parkinson's disease symptoms, an Oregon Health & Science University study has 
found.

Scientists at the OHSU Parkinson Center of Oregon found that methylphenidate, 
known commercially as Ritalin, bolsters
the effects of levodopa, a drug converted in the brain to dopamine. 
Methylphenidate inhibits the reabsorption of
dopamine into nerve cells, increasing the neurotransmitter's potency.

Parkinson's disease is caused by a deficiency of nerve cells that produce 
dopamine.

A parallel study by Parkinson center researchers found that paroxetine, a 
popular antidepressant best known under the
brand name Paxil, doesn't augment the effects of levodopa and has little 
benefit in reducing physical symptoms of
Parkinson's disease.

Paroxetine is a selective serotonin reuptake inhibitor, or SSRI, a class of 
antidepressants that block the reabsorption
of another neurotransmitter, serotonin, into nerve cells. Researchers studied 
it because laboratory evidence has
suggested the serotonin transporter, the system through which serotonin is 
reabsorbed into nerve cells, may take up
dopamine as well.

"Both studies looked at the effects of these drugs on Parkinson's disease," 
said John "Jay" G. Nutt, M.D., professor of
neurology, and physiology and pharmacology, OHSU School of Medicine, and 
director of the Parkinson center. He also is
director of the Parkinson's Disease Research, Education, and Clinical Center 
(PADRECC) at the Portland Veterans Affairs
Medical Center. The studies were presented last week at the 56th annual meeting 
of the American Academy of Neurology in
San Francisco.

Ritalin, the drug used in the methylphenidate study, "increases the effects of 
levodopa," Nutt said, while paroxetine
didn't affect Parkinson's disease symptoms. However, paroxetine, when taken 
without levodopa, did increase the walking
speed of Parkinson's patients.

"There was no evidence that (paroxetine) made Parkinson's disease worse, as 
some clinicians have suggested," Nutt said.
"If that occurred, it probably wasn't by negatively impacting dopamine's 
effects."

In the Ritalin study, 14 Parkinson's disease patients with fluctuating 
responses to levodopa were examined. All
received two-hour levodopa infusions at either minimum or maximum doses for 
four consecutive days, but some also
received oral doses of Ritalin. Participants were then tested for symptoms of 
Parkinsonism, including tapping and
walking speeds; dyskinesia or involuntary movements such as twitching, nodding 
and jerking; mood, anxiety and fatigue;
and sitting blood pressure.

Ritalin amplified the effects of levodopa, particularly for those given minimum 
doses of levodopa. It increased, from
36 percent to 86 percent, the number of patients responding to levodopa, and it 
boosted the duration of levodopa
response as measured by tapping and walking tests. But the severity of 
dyskinesia, a side effect of levodopa therapy,
did not rise.

In addition, Ritalin decreased another levodopa side effect ? hypotension, or 
low blood pressure ? and it enhanced
improvements levodopa made in mood and decreased fatigue. Adverse effects, in 
general, were minimal, and the drug had
no effect when given alone to Parkinson's disease patients.

The study's findings do more than show that Ritalin improves patients' 
responses to levodopa, Nutt said. They confirm
the importance of the dopamine transporter, the system through which dopamine 
is reabsorbed into nerve cells, and shows
that the transporter may be a target for other levodopa-boosting drugs.

"It may be that by blocking the dopamine transporter with one drug or another, 
we can augment the effects of levodopa
and get better control of Parkinson's disease," he said.

Pharmaceutical companies already are looking at other drugs that may block the 
transporter, Nutt added. And the OHSU
Parkinson Center will continue to study Ritalin, including whether more doses 
promotes levodopa response throughout the
day.

"The first study is proof of principle ? blocking the dopamine transporter," 
Nutt said. "Now the question is, would
Ritalin be the drug to do that? That's not clear."

The paroxetine study was conducted on 14 people with varying severity of 
Parkinson's disease. Each was given two-hour
levodopa infusions; some also received paroxetine for two weeks while the rest 
were given a placebo. The subjects were
then scored for tapping rate, tremor and dyskinesia, as well as walking speed.

Paroxetine, when given with levodopa, didn't affect tapping, dyskinesia or 
tremor, according to the findings. In fact,
six people reported worse balance while on paroxetine.

Nutt's Ritalin study collaborators were Julie H. Carter, R.N., A.N.P., 
associate professor of neurology, OHSU School of
Medicine, and associate director of the Parkinson center; and Gary J. Sexton, 
Ph.D., associate professor of public
health and preventive medicine, OHSU School of Medicine. Paroxetine study 
collaborators were Kathryn A. Chung, M.D.,
assistant professor of neurology, OHSU School of Medicine and the Parkinson 
center, and PADRECC, Portland VA Medical
Center.

###

Both studies were supported by the National Institute of Neurological Disorders 
and Stroke, National Institutes of
Health; PADRECC; and the National Parkinson Foundation.

To access all OHSU news releases, visit 

SOURCE: EurekAlert, DC - May 6, 2004


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